This invention pertains to improved leak detectors of the mass spectrometer type, and in particular neon gas leak detectors.
Instruments for detecting trace amounts of a leak gas in the presence of one or more background gases are well known. Frequently, it is desirable from a cost and maintenance standpoint, to convert leak detection instruments so that they can read gases which differ from those gases that the instrument was designed to detect. This conversion process is not always a straightforward one. For example, in the mass-spectrometer type of gaseous leak detector, the well known equation for the radius of internal trajectory of the detected gas, ##EQU1## is not in itself sufficient to assure adequate particle collection rates in a modified detector. If, for example one wished to use a helium gas leak detector to measure neon gas, (which has a larger mass, 20 mass units, as opposed to the four mass units of helium) the controllable operating parameters of the instrument (referred to in the preceeding equation) are the magnetic field strength, B (in 10.sup.-4 gauss), and accelerating voltage v (in volts), assuming a given instrument having a fixed, defined radius r (in meters). The proportionality constant K and electronic charge e (in coulombs) are not controllable. Thus, for an existing instrument, i.e., an instrument of fixed particle trajectory radius r, a change in mass m is typically compensated for by a change in magnetic field B, or accelerating voltage v or both. However, the theory of detector operation is often inadequate to produce a successful conversion for a given practical instrument; for example, the converted instrument might not provide adequate particle collection rates.
It is therefore an object of the present invention to provide an inexpensive arrangement for converting a helium gas leak detector to a neon gas leak detector.
It is another object of the present invention to provide a conversion arrangement having improved detectedparticle collection efficiencies.
Another object of the present invention is to provide a conversion arrangement that requires a minimum modification to existing equipment.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.